Armored optical fiber cable

ABSTRACT

An optical communication cable subassembly includes a cable core having optical fibers each comprising a core surrounded by a cladding, buffer tubes surrounding subsets of the optical fibers, and a binder film surrounding the buffer tubes. Armor surrounds the cable core, the binder film is bonded to an interior of the armor, and water-absorbing powder particles are provided on an interior surface of the binder film.

PRIORITY APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/702,201, filed on Sep. 12, 2017, which is a divisional of U.S. patentapplication Ser. No. 14/829,819, filed on Aug. 19, 2015, now U.S. Pat.No. 9,791,652, which is a continuation of U.S. patent application Ser.No. 14/315,872, filed on Jun. 26, 2014, now U.S. Pat. No. 9,140,867,which claims the benefit of priority to 61/864,104, filed on Aug. 9,2013, the content of which is relied upon and incorporated herein byreference in entirety.

BACKGROUND

The disclosure relates generally to optical communication cables andmore particularly to optical communication cables including one or morefeatures configured to protect the cable body from interaction withcomponents located within the cable jacket. Optical communication cableshave seen increased use in a wide variety of electronics andtelecommunications fields. Optical communication cables may contain orsurround one or more optical communication fibers. The cable providesstructure and protection for the optical fibers within the cable.

SUMMARY

One embodiment of the disclosure relates to an optical communicationcable that includes a core, armor surrounding the core, a jacketsurrounding and bonded to the armor, and a binder film also surroundingthe core and interior to the armor. The core includes buffer tubessurrounding sets of optical fibers and a central strength member. Thebuffer tubes are stranded around the central strength member in apattern of stranding including reversals in lay direction of the buffertubes and the binder film holds the buffer tubes in position. The binderfilm is bonded to an interior of the armor, thereby providing a quickaccess capability to access the core via simultaneous removal of thebinder film when the armor and jacket are removed.

An optical communication cable subassembly includes a cable core havingoptical fibers each comprising a core surrounded by a cladding, buffertubes surrounding subsets of the optical fibers, and a binder filmsurrounding the buffer tubes. Armor surrounds the cable core, the binderfilm is bonded to an interior of the armor, and water-absorbing powderparticles are provided on an interior surface of the binder film.Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from the description or recognized by practicing theembodiments as described in the written description and claims hereof,as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understand the natureand character of the claims.

The accompanying drawings are included to provide a furtherunderstanding and are incorporated in and constitute a part of thisspecification. The drawings illustrate one or more embodiment(s), andtogether with the description serve to explain principles and operationof the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fiber optic cable according to anexemplary embodiment.

FIG. 2 is a cross-sectional view of the fiber optic cable of FIG. 1according to an exemplary embodiment.

FIG. 3 is a detailed cross-sectional view of a portion of the fiberoptic cable of FIG. 1 according to an exemplary embodiment.

FIG. 4 is a cross-sectional view of a fiber optic cable according toanother exemplary embodiment.

FIG. 5 is a perspective view of a fiber optic cable according to anexemplary embodiment.

FIG. 6 is a cross-sectional view of a fiber optic cable according toanother exemplary embodiment.

FIG. 7 is a cross-sectional view of an interface of armor according toanother exemplary embodiment.

DETAILED DESCRIPTION

Referring generally to the figures, various embodiments of an opticalcommunication cable (e.g., a fiber optic cable, an optical fiber cable,etc.) are shown. In general, the cable embodiments disclosed hereininclude a cable jacket or body typically formed from a polymer material(e.g., a medium density polyethylene material). A group of opticalfibers is surrounded by a protective, armor or reinforcement material(e.g., a corrugated metal sheet or sheets of material), and the armoredgroup of optical fibers is positioned in a central channel of the cablejacket. Generally, the cable jacket provides physical support andprotection to the optical fibers within the cable, and the armormaterial provides additional reinforcement to the optical fibers withinthe cable jacket.

The sheet or sheets of armor material includes an overlapped portioncreated by the overlapping of opposing edges of the armor material asthe armor extends around the optical fibers. The overlapped section and,in particular, the exposed lateral edge of the upper portion of theoverlap may contact the inner surface of the cable jacket that definesthe channel of the cable jacket. This interaction or contact may tend tocreate a split within the cable jacket particularly upon twisting of thecable (such splitting may be referred to in the field as “cablezippering”).

The cable jacket embodiments discussed herein include at least oneprotective member or feature positioned within the wall of the cablejacket that resists or prevents splitting caused by the armor overlapfrom compromising the integrity of the cable jacket. The protectivemember is positioned adjacent to and, in some embodiments, is in contactwith the overlap of the armor material and/or the exposed lateral edgeof the armor. The protective member may act to resist, limit or preventsplit formation or split propagation that may otherwise be caused by thecontact between the armor overlap and the material of the cable jacket.

In some embodiments, the material of the protective member may be morerigid than the primary material of the cable jacket. In suchembodiments, the discontinuity at the interface of the two differentmaterials may stop split propagation from continuing through to theouter surface of the cable jacket. In some other embodiments, thematerial of the protective member may be a compliant material that isless rigid than the primary material of the cable jacket. In suchembodiments, the protective member may function as a compliant bufferthat absorbs movement of the armor overlap rather than allowing a splitto form in the primary material of the cable jacket.

In various embodiments discussed herein, the protective member may beformed along with the cable jacket in a single production step. Forexample, the protective member may be coextruded with the extrudedmaterial of the cable jacket. In such embodiments, the embeddedprotective member embodiments discussed herein may avoid the need foradditional manufacturing steps to cover up or otherwise blunt the armoroverlap.

Referring to FIGS. 1 and 2, an optical communication cable, shown ascable 10, is shown according to an exemplary embodiment. Cable 10includes a cable jacket, shown as cable jacket 12, having an innersurface 14 that defines a channel, shown as central bore 16. A pluralityof optical transmission elements, shown as optical fibers 18, arelocated within bore 16. Generally, cable 10 provides structure andprotection to optical fibers 18 during and after installation (e.g.,protection during handling, protection from the elements, protectionfrom vermin, etc.).

In the embodiment shown in FIGS. 1 and 2, bundles of optical fibers 18are located within buffer tubes 20. One or more filler rods 22 are alsolocated within bore 16. Filler rods 22 and buffer tubes 20 are arrangedaround a central support rod 24 formed from a material such asglass-reinforced plastic or metal. In some embodiments, helically woundbinders 26 are wrapped around buffer tubes 20 and filler rods 22 to holdthese elements in position around support rod 24. A barrier material,such as water barrier 28, is located around the wrapped buffer tubes 20and filler rods 22. In other embodiments, a thin-film binder may beused, which may additionally be a water barrier.

An armor layer 30, is located outside of water barrier 28 or thin-filmbinder. Armor layer 30 extends around the interior elements (includingoptical fibers 18) of cable 10 such that armor layer 30 surround opticalfibers 18. Armor layer 30 generally extends all or substantially all ofthe axial length of cable 10. Armor layer 30 generally provides anadditional layer of protection to fibers 18 within cable 10, and mayprovide resistance against damage (e.g., damage caused by contact orcompression during installation, damage from the elements, damage fromrodents, etc.)

As shown best in FIGS. 2 and 3, armor layer 30 has a first lateral edge32 and a second lateral edge 34. In the embodiment shown, lateral edges32 and 34 are substantially parallel to the longitudinal axis of cable10 and of fibers 18. Referring to FIGS. 2 and 3, armor layer 30 ispositioned such that first lateral edge 32 passes over or overlapssecond lateral edge 34. In this arrangement, a section 36 of armor layer30 adjacent first lateral edge 32 is located above a section 38 of armorlayer 30 adjacent second lateral edge 34 forming an overlap portion 40.In one embodiment, an upper surface of section 38 is in contact with alower surface of section 36 such that the thickness, T2 (i.e., thedimension in the radial direction shown in FIGS. 2 and 3) of overlapportion 40 is about twice the thickness the material of armor layer 30.With section 38 located below section 36, the upper corner 42 of lateraledge 32 defines the outer most corner of armor layer 30.

In various embodiments, armor layer 30 may be formed from a variety ofstrengthening or damage resistant materials. In the embodiment shown inFIG. 1, armor layer 30 is formed from a corrugated sheet of metalmaterial having an alternating series of ridges and troughs. Thecorrugations may be oriented so that ridges formed thereby are directedaway from the lengthwise axis of the cable. Further the sheets may becorrugated in a coordinated manner such that overlaying portions of thesheets have intermeshing features of the corrugations, thereby providingflexibility to the sheets in bending (via the corrugations in general)and coupling the sheets to one another via the intermeshing. In oneembodiment, the corrugated metal is steel. In other embodiments, thecorrugated metal may additionally serve as a ground conductor for thecable, such as with copper or aluminum armor. In other embodiments,other non-metallic strengthening materials may be used. For example,armor layer 30 may be formed from a fiberglass yarns (e.g., coatedfiberglass yarns, rovings, etc.). In some embodiments, armor layer 30may be formed from plastic materials having a modulus of elasticity over2 GPa, and more specifically over 2.7 GPa. Such plastic armor layers maybe used to resist animal gnawing and may include animal/pest repellantmaterials (e.g., a bitter material, a pepper material, synthetic tigerurine, etc.). In one embodiment, cable 10 could include a nylon 12 layeracting to resist termites.

Referring to FIGS. 2 and 3, cable jacket 12 generally includes a primaryjacket portion 50 and a secondary jacket portion, shown as splitresistant feature 52. Feature 52 is an elongate member or structureembedded within the material of primary jacket portion 50 of cablejacket 12. In various embodiments, feature 52 is a contiguous memberthat extends the length of cable jacket 12 between the first and secondends of the cable. In general, primary jacket portion 50 is made from afirst material, and feature 52 is made from a second material that isdifferent from the first material. Feature 52 includes an inner surface54, and feature 52 is positioned such that inner surface 54 may becontiguous with inner surface 14 of cable jacket 12 such that innersurface 54 and inner surface 14 define channel 16. In one embodiment,feature 52 is coextruded along with primary jacket portion 50 such thatthe transition between inner surface 54 and inner surface 14 is asubstantially smooth transition.

Feature 52 is positioned within primary jacket portion 50 such thatinner surface 54 is aligned with and is generally adjacent to overlapportion 40, first lateral edge 32 and corner 42. Feature 52 is alignedwith overlap portion 40, first lateral edge 32 and corner 42 such thatinner surface 54 is located between overlap portion 40 and exteriorsurface 58 of cable jacket 12. In the embodiment shown in FIG. 3, innersurface 54 of feature 52 is located exterior to (i.e., above in theorientation of FIG. 3) overlap portion 40, first lateral edge 32 andcorner 42. In a specific embodiment, inner surface 54 of feature 52 isin contact with the outer surface of overlap portion 40 and/or corner 42of first lateral edge 32. In another embodiment, a layer of the materialof jacket portion may be located between inner surface 54 of feature 52and the outer surface of overlap portion 40 and corner 42 of firstlateral edge 32. In such embodiments, even though inner surface 54cannot directly contact overlap portion 40 because of the interveningmaterial layer, such as when the feature 52 is fully embedded (i.e.,completely surrounded when viewed in cross-section) in the primaryjacket portion 50, inner surface 54 may be located a small distance(e.g., less than 1 mm or less than 0.5 mm) from the outer surface ofoverlap portion 40 and corner 42 of first lateral edge 32 such thatsplit formation or propagation is resisted (see, e.g., FIG. 8).

Feature 52 acts to resist or prevent split formation or propagationwithin the material primary jacket portion 50 of cable jacket 12. Invarious embodiments, the material of primary jacket portion 50 may besusceptible to split formation if portions of armor overlap 40 contactthe material of primary jacket portion 50. Such contact may occur duringmovements such as twisting movements typical during cable installation.However, in the embodiments discussed herein, feature 52 is sized,shaped, positioned and/or has certain material properties that allowfeature 52 to prevent/limit/resist split formation or propagation. Thus,by positioning feature 52 as shown in FIG. 3, adjacent to overlapportion 40, feature 52 is able to interact with overlap 40 duringmovement of cable 10 and to resist split formation/propagation.

In a various embodiments, the width, W1, (i.e., the circumferentialdimension in the circular embodiment of FIG. 2) of inner surface 54 offeature 52 is sized relative to the width, W2, of overlap 40 such thatfeature 52 remains aligned with overlap 40 even if rotation of armorlayer 30 relative to cable jacket 12 occurs during jacket extrusion. Insuch embodiments, the width, W1, of inner surface 54 of feature 52 isgreater than the width, W2, of overlap 40. In various embodiments, W1 isbetween 1 mm and 20 mm and specifically between 3 mm and 10 mm, and W2is between 2 mm and 10 mm and specifically is between 3 mm and 5 mm. Inround cables, the width W1 covers an arc length of at least 2° and/orless than 20°, such as at least 3° and/or less than 15°, about thecenter of the cable.

Feature 52 is positioned such that feature 52 does not extend all of theway through primary jacket portion 50 from channel 16 to outer surface58 of cable 10. Thus, the thickness, T1, of feature 52 (i.e., the radialdimension of feature 52 in the circular embodiment of FIG. 2) is lessthan the thickness, T4, of primary jacket portion 50. In thisembodiment, feature 52 extends from channel 16 outward a portion of thedistance to outer surface 58 such that a section 60 of primary jacketportion 50 is located between an outermost surface 62 of feature 52 andouter cable surface 58.

In various embodiments, the material of feature 52 may be selectedrelative to the material of primary jacket portion 50 to resist/preventsplit formation or propagation. In one embodiment, the modulus ofelasticity of feature 52 may be greater than the modulus of elasticityof the material of primary jacket portion 50. In this embodiment,feature 52 may be formed from a material with relatively low bondstrength to the material of primary jacket portion 50. In thisembodiment, it is believed that the low bonding at interface 56 betweenfeature 52 and primary jacket portion 50 will stop the propagation of asplit that may be created within the material of feature 52 viainteraction with overlap 40. By stopping split propagation at interface56, a spilt is not permitted to extend through to outer surface 58 ofcable jacket 12, and thus the feature 52 acts to maintain the wall ofcable jacket 12 intact.

In such embodiments, the modulus of elasticity of the material offeature 52 is between 1.0 GPa and 2.0 GPa, specifically between 1.0 GPaand 1.5 GPa, and more specifically is about 1.2 GPa. In suchembodiments, the modulus of elasticity of the material of primary jacketportion 50 is between 100 MPa and 800 MPa, specifically between 0.2 GPaand 0.4 GPa, and more specifically is about 0.31 GPa. In variousembodiments, the modulus of elasticity of feature 52 is between 2 timesand 10 times the modulus of primary jacket portion 50, specifically isbetween 3 times and 6 times the modulus of primary jacket portion 50,and more specifically is between 4 times the modulus of primary jacketportion 50.

In various such embodiments, primary jacket portion 50 is formed from anextruded polymer material, and feature 52 is formed from an extrudedpolymer material. In a specific embodiment, primary jacket portion 50 isformed from (e.g., comprises, consists at least 50% of by volume,includes as the major constituent) an extruded medium densitypolyethylene material (e.g., a polyethylene material having a densitybetween 0.939 to 0.951 g/cm³), and feature 52 is formed from an extrudedpolypropylene material. In a specific embodiment, feature 52 is formedfrom an extruded polypropylene material that includes a low percentageof polyethylene. The small amount of polyethylene within feature 52provides sufficient bonding with the material of primary jacket portion50 allowing for proper coextrusion of feature 52 and primary jacketportion 50, while maintaining sufficient dissimilarity and low bondingto cease split propagation at interface 56. In various embodiments, thematerial of feature 52 may include between 2% and 20% polyethylene,specifically between 5% and 15% polyethylene and more specifically about9% polyethylene. In such embodiments, these combinations of polyethyleneand polypropylene for feature 52 may act to provide sufficientdiscontinuity at interface 56 to limit split propagation while providingsufficient bonding between the material of feature 52 and thesurrounding material.

In some embodiments, the primary jacket portion 50 includespolyethylene, such as where polyethylene is the major constituent of theprimary jacket portion 50, such as where the primary jacket portion 50mostly consists of polyethylene by volume, such as greater than 50%polyethylene by volume, at least 70% polyethylene by volume, etc. Insome such embodiments, the feature 52 is formed from ahighly-plasticized polymer, such as a highly-plasticized polyvinylchloride, polyurethane, polypropylene, or other highly-plasticizedpolymer. Softness and flexibility provided by the plasticizer maymitigate crack initiation and propagation therethrough. In otherembodiments, the feature 52 is formed from a highly-filled polymer, suchas a highly filled polyvinyl chloride, polyurethane, polypropylene, orother highly-filled polymer. Particles of the filler material andinterfaces between the particles and the base material may arrest orlimit crack propagation through the polymer.

In the embodiments of cable 10 in which the modulus of feature 52 isgreater than the modulus of primary jacket portion 50, the thickness offeature 52 may be less than the thickness of overlap portion 40 becausein these embodiments split propagation is limited by the discontinuityof material at interface 56. In such embodiments, the thickness, T1,(i.e., the radial dimension in the circular embodiment of FIG. 3) offeature 52 is between 0.1 mm and 0.5 mm. In such embodiments, thickness,T2, of overlap 40 is between 0.2 mm and 1.1 mm. In a specificembodiment, armor layer 30 is formed from a corrugated metal materialand thickness, T2, is between 0.6 mm and 1.2 mm, and more specificallyis between 0.78 mm and 1.04 mm. In another specific embodiment, armorlayer 30 is formed from a non-corrugated metal material, and thickness,T2, is between 0.2 mm and 0.4 mm, and more specifically is between 0.28mm and 0.34 mm.

In other embodiments, the modulus of elasticity of feature 52 may beless than the modulus of elasticity of the material of primary jacketportion 50. In this embodiment, feature 52 may be formed from acompliant material. In this embodiment, it is believed that thecompliant material with resist or prevent split formation by deformingupon interaction with overlap portion 40 acting as a buffer to preventdisplacement and resulting split formation within the more rigidmaterial of primary jacket portion 50.

In such embodiments, the modulus of elasticity of the material offeature 52 is between 10 MPa and 50 MPa, specifically between 15 MPa and25 MPa, and more specifically between 18 MPa and 19 MPa; and/or no morethan half that of the material of primary jacket portion 50, such as nomore than a third that of the material of primary jacket portion 50,such as no more than a quarter that of the material of primary jacketportion 50. In such embodiments, the modulus of elasticity of thematerial of primary jacket portion 50 is between 0.1 GPa and 0.8 GPa,specifically between 0.2 GPa and 0.4 GPa, and more specifically is about0.31 GPa. In various embodiments, primary jacket portion 50 is formedfrom an extruded polymer material, and feature 52 is formed from anextruded polymer material. In a specific embodiment, primary jacketportion 50 is formed from an extruded medium density polyethylenematerial, and feature 52 is formed from an extruded thermoplasticelastomer material (TPE). In one embodiment, the TPE material may beAffinity GA 1950, available from the Dow Chemical Company.

In the embodiments of cable 10 in which the modulus of feature 52 isless than the modulus of primary jacket portion 50, the thickness offeature 52 may be equal to or greater than the thickness of overlapportion 40 because in some such embodiments split formation is resistedvia compliance of feature 52, such as via stress isolation thereby. Insuch embodiments, the thickness, T1, (i.e., the radial dimension in thecircular embodiment of FIG. 3) of feature 52 is between 0.5 mm and 1.1mm. In such embodiments, thickness, T2, of overlap 40 is between 0.2 mmand 1.1 mm. In a specific embodiment, armor layer 30 is formed from acorrugated metal material and thickness, T2, is between 0.6 mm and 1.2mm, and more specifically is between 0.78 mm and 1.04 mm. In anotherspecific embodiment, armor layer 30 is formed from a non-corrugatedmetal material, and thickness, T2, is between 0.2 mm and 0.4 mm, andmore specifically is between 0.28 mm and 0.34 mm.

In addition to providing split resistance via feature 52, cable jacket12 may include a plurality of additional elongate members, shown asaccess features 70 and 72. In general access features 70 and 72 areelongate members or structures embedded within the material of primaryjacket portion 50 of cable jacket 12. In various embodiments, accessfeatures 70 and 72 are contiguous members that extend the length ofcable jacket 12 between the first and second ends of the cable.

In general, primary jacket portion 50 is made from a first material, andaccess features 70 and 72 are made from a second material that isdifferent from the first material. The difference in materials providesa discontinuity or weakness within cable jacket 12 at the location ofaccess features 70 and 72. These discontinuities provide an access pointthat allows a user of cable 10 to split cable jacket 12 when access tooptical fibers 18 is desired. In various embodiments, access features 70and 72 may be formed from a material (e.g., a polypropylene/polyethyleneblend as discussed above) with low bonding relative to the material ofprimary jacket portion 50 that allows for jacket splitting by the user.In various embodiments, access features 70 and 72 and split resistantfeature 52 may be formed (e.g., coextruded) as described in US2013/0051743, filed Oct. 25, 2012, which is incorporated herein byreference in its entirety.

In various embodiments as shown in FIG. 2, access features 70 and 72 areformed from the same material as feature 52, and access feature 70 iscontiguous with feature 52 such that access feature 70 and feature 52form a single, continuous elongated member extending the length of cable10. In this embodiment, access feature 70 and feature 52 may be extrudedtogether in a single extrusion process. In this embodiment, outersurface 62 of feature 52 is continuous with outer surface 74 of accessfeature 70, and section 60 of primary jacket portion 50 is located aboveboth outer surface 74 and outer surface 62. In various embodiments, thethickness, T3, of contiguous features 52 and 70 is the distance frominner surface 54 to the outer most point of surface 74, and thethickness, T4, of primary jacket portion 50 is the distance between theinner surface of primary jacket portion 50 and outer surface 58. Invarious embodiments, T3 is at least about 30% (such as at least a third)and/or no more than about 95% (such as less than all) of T4 (onaverage), such as between 50% and 95% of T4, specifically is between 70%and 90% of T4, and more specifically is between 80% and 90% of T4. In aspecific embodiment, T3 is about 85% of T4.

In various embodiments, the thickness T4 of primary jacket portion 50 isbetween 0.5 mm and 5 mm, specifically between 1.0 mm and 2.0 mm, andmore specifically is between 1.0 mm and 1.5 mm. In a specificembodiment, the thickness T4 of primary jacket portion 50 is about 1.3mm. In such embodiments, the thickness T3 of contiguous features 52 and70 is between 0.4 mm and 4.5 mm, specifically is between 1.0 mm and 1.8mm and more specifically is between 1.1 mm and 1.5 mm. In a specificembodiment, the thickness T4 of primary jacket portion 50 is about 1.3mm, and the thickness T3 of contiguous features 52 and 70 is about 1.1mm.

In various embodiments, features 52, 70 and 72 may be formed from apolypropylene/polyethylene blended polymer material as discussed above,and in such embodiments, primary jacket portion 50 may be formed from amedium-density polyethylene material. In such an embodiment, the lowbonding of the material of contiguous features 52 and 70 with thematerial of primary jacket portion 50 may function to limit splitpropagation past interface 56 as discussed above, and the low bonding ofthe material features 70 and 72 with the material of primary jacketportion 50 allows for splitting of jacket 12.

In other embodiments, access features 70 and 72 may be formed from afirst material and feature 52 may be formed from a different secondmaterial. In one such embodiment, access features 70 and 72 may beformed from a material with low bonding relative to the material ofprimary jacket portion 50 that allows for jacket splitting by the user(e.g., a polypropylene/polyethylene blend as discussed above), andfeature 52 may be formed from a compliant material such as a TPEmaterial. In this embodiment, an interface 78 (shown by the dotted linein FIG. 3) may be present between split resistant feature 52 and accessfeature 70.

As shown in FIG. 3, the width W3 of access feature 70 (e.g., maximumtangential dimension) is less than width W1 of inner surface 54 of splitresistant feature 52. In various embodiments, W3 is between 0.1 mm and0.5 mm, specifically between 0.2 mm and 0.4 mm, and more specifically isabout 0.3 mm. As discussed above, in various embodiments, W1 is between1 mm and 20 mm and specifically between 3 mm and 10 mm, and W2 isbetween 2 mm and 10 mm and specifically is between 3 mm and 5 mm. Invarious embodiments W1 is between 5 times and 50 times greater than W3,and specifically is between about 10 times and 20 times greater than W3.

In the embodiment shown in FIG. 2, both access feature 70 and splitresistant feature 52 are located generally at the 12 o'clock position,and access feature 72 is located approximately 180 degrees from feature70 at the 6 o'clock position. Spacing access features 70 and 72 by 180degrees may allow for maximized access to fibers 18 following jacketsplitting.

Referring to FIG. 4, a cable 100 is shown according to an exemplaryembodiment. Cable 100 is substantially similar to cable 10 except asdiscussed herein. Cable 100 includes access features 102 and 104embedded within the material of primary jacket portion 50. In thisembodiment, access features 102 and 104 function same as features 70 and72 discussed above except that they are spaced apart from feature 52. Inthe specific embodiment shown, feature 52 is located at the 12 o'clockposition aligned with and adjacent armor overlap 40, access feature 102is located approximately 90 degrees clockwise from feature 52 at the 3o'clock position, and access feature 104 is located approximately 270degrees clockwise from feature 52 at the 9 o'clock position.

Referring to FIG. 5, a cable 110 is shown according to an exemplaryembodiment. Cable 110 includes split resistant feature 52 and accessfeatures 70 and 72 located within cable jacket 12 and is substantiallysimilar to cable 10 except as discussed herein. Cable 110 includes anelongate strengthening member, shown as rod 112, located within cablejacket 12 that runs the length of cable jacket 12. Rod 112 is formedfrom a material that is more rigid than the material of cable jacket 12.In various embodiments, the strengthening member is metal, braidedsteel, glass reinforced plastic, fiber glass, fiber glass yarns or othersuitable material. Cable 110 includes a stack 114 of a plurality ofoptical transmission elements, shown as fiber optic ribbons 116, locatedwithin the channel of cable jacket 12.

Referring to FIG. 6, a cable 120 is shown according to an exemplaryembodiment. Cable 120 is substantially similar to cable 10 except asdiscussed herein. Cable 120 includes two split resistant features 52,and two access features 70 contiguous with each feature 52. In theembodiment shown, cable 120 includes a two-part armor layer 122 (e.g.,clam shell armor layer) including two armor overlap portions 40. Splitresistant features 52 and access features 70 are located adjacent tooverlap portions 40. In this embodiment, armor layer 122 includes afirst section 124 and a second section 126. In the embodiment shown,first section 124 and second section 126 are semi-cylindrical orarch-shaped elements with second section 126 received partially withinfirst section 124 creating overlap portions 40. In other embodiments,the first section may be outside the second section on one side and viceversa on the other. Use of two split resistant features 52 may alsofacilitate tearing of a section of the jacket therebetween to assistaccessing the contents of the cable 120.

In this embodiment, both of the access features 70 are positionedaligned with overlap sections 40. This positioning allows cable jacket12 to be opened and for armor layer 122 to be opened (e.g., byseparating first armor section 124 from second armor section 126) at thesame time or with the same opening action that opens cable jacket 12.

In some such embodiments, a bonding agent (e.g., chemical bonding agentsuch as Maleic anhydride, ethylene acrylic acid copolymer; flametreatment changing the surface chemistry; surface roughening increasingthe surface area) may be used in or adjoining cable jacket 12 toincrease bonding between the inner surface of cable jacket 12 and theouter surface of armor layer 122, between either or both of the firstand second sections 124, 125 and the jacket. The bonding between cablejacket 12 and armor layer 122 may facilitate removal of both layerstogether with a single opening action. The bonding agent may also act toprevent relative sliding of edges of two-piece armor layer 122, and thebonding agent may also be used to prevent relative sliding of thecomponents of any of the other embodiments disclosed herein. The bondingagent may be mixed in the primary jacketing material, positioned on thesurface of the armor, or both.

In one embodiment, cable 120 includes a binder layer, shown as thin-filmbinder 128, positioned around buffer tubes 20. Generally, thin-filmbinder 128 is a material layer surrounding and binding together buffertubes 20 within central channel 16. In one embodiment, cable 120 and/orthin-film binder 128 may be binders/cables as disclosed in U.S.application Ser. No. 13/790,329, filed Mar. 8, 2013, which isincorporated herein by reference in its entirety. In some embodiments,the outer surface of binder 128 is bonded to the inside surface of armorlayer 122 (e.g., with glue, bonding agent, chemical adhesion) so thatthe access features 70 may be used to tear open cable jacket 12, armor122, and binder 128 in a single tearing action to access contents ofcable 120 (e.g., buffer tubes 20 of optical fibers 18, a stack of fiberoptic ribbons, tight-buffered fibers, or other arrangements of opticalfibers). The binder film 128 may also serve as a carrier forwater-blocking materials, such as SAP partially embedded on the insidesurface of the film 128. The binder film 128 is substantially thinnerthan a jacket, such as less than a fifth of the jacket 12, less than atenth, or even less than a twentieth. The binder film 128 may beextruded, and may include polyethylene, polypropylene, or anotherpolymer as the primary constituent thereof. Tension in the binder film128 may hold the contents of the core together as the binder film 128cools and contracts following extrusion. In other embodiments, thebinder film 128 is not bonded to the armor.

In the embodiments discussed above, primary jacket portion 50 is formedfrom a single layer of extruded polymer material (e.g., a medium-densitypolyethylene material), and in other embodiments, jacket 12 may includemultiple layers of materials. In various embodiments, primary jacketportion 50 may be a variety of materials used in cable manufacturingsuch as polyvinyl chloride (PVC), polyvinylidene difluoride (PVDF),nylon, polyester or polycarbonate and their copolymers. In addition, thematerial of primary jacket portion 50 may include small quantities ofother materials or fillers that provide different properties to thematerial of primary jacket portion 50. For example, the material ofprimary jacket portion 50 may include materials that provide forcoloring, UV/light blocking (e.g., carbon black), burn resistance, etc.

Referring now to FIG. 7, an interface 210 between lateral edges 214, 216of armor 212 is shown. The lateral edges 214, 216 may be from the samearmor sheet (see generally FIG. 2), or from separate armor sheets (seegenerally FIG. 6). According to an exemplary embodiment, the interface210 includes a seat 218 in which one of the lateral edges 216 is held. Ajacket 220 holds the lateral edge 216 in the seat 218 during operationof the corresponding cable. However, the seat 218 also allows thelateral edge 216 to be withdrawn from the seat 218 (vertically as shownin FIG. 7), such as with minimal resistance from the seat 218 itself(e.g., less than 15 N per meter length), such as if the jacket 220 ispulled apart from the inside, where the lateral edges are drawn apart inopposite directions tangential to the interface. Put another way, theseat 218 may lock the lateral edges 214, 216 together in some degrees offreedom, such as preventing relative rotations, relative radialtranslation (in the horizontal direction of FIG. 7), and relativelengthwise translation (limited via aligned corrugations between theoverlaying pieces of armor 212, into and out of FIG. 7), but may allowrelative tangential translation (i.e., pulling apart, in the verticaldirection of FIG. 7).

In such an embodiment, the interface 210 may also be aligned with tearfeatures and/or anti-zipper features 222 in the jacket 220, whichmitigate the likelihood of inadvertent zippering and/or also mayfacilitate purposeful tearing open of the jacket 220. The net force topull the jacket 220 and armor 212 apart may be less than 80 N toinitiate a tear through the jacket 220 along the tear features and/oranti-zipper features 222 on a free end of the cable. As shown in FIG. 7,visual and/or tactile indicia on the exterior of the respective cable(e.g., either cable in FIGS. 2 and 6) may help users locate theinterface 210. The indicia may include raised portions 224 of the jacket220, such as bumps or elongate ridges on the jacket 220.

While the specific cable embodiments discussed herein and shown in thefigures relate primarily to cables that have a substantially circularcross-sectional shape defining substantially cylindrical internallumens, in other embodiments, the cables discussed herein may have anynumber of cross-section shapes. For example, in various embodiments,cable jacket 12 may have a square, rectangular, triangular or otherpolygonal cross-sectional shape. In such embodiments, the channel orbore of the cable may be the same shape or different shape than theshape of cable jacket 12. In some embodiments, cable jacket 12 maydefine more than one channel. In such embodiments, the multiple channelsmay be of the same size and shape as each other or each may havedifferent sizes or shapes.

The optical fibers discussed herein may be flexible, transparent opticalfibers made of glass or plastic. The fibers may function as a waveguideto transmit light between the two ends of the optical fiber. Opticalfibers may include a transparent core surrounded by a transparentcladding material with a lower index of refraction. Light may be kept inthe core by total internal reflection. Glass optical fibers may comprisesilica, but some other materials such as fluorozirconate,fluoroaluminate, and chalcogenide glasses, as well as crystallinematerials, such as sapphire, may be used. The light may be guided downthe core of the optical fibers by an optical cladding with a lowerrefractive index that traps light in the core through total internalreflection. The cladding may be coated by a buffer and/or anothercoating(s) that protects it from moisture and/or physical damage. Thesecoatings may be UV-cured urethane acrylate composite materials appliedto the outside of the optical fiber during the drawing process. Thecoatings may protect the strands of glass fiber. In some contemplatedembodiments, jackets and armor disclosed herein may be used with cablesand conduits, such as ducts or conductive-copper carrying cable, whereoptical fibers may not be included.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is in no way intendedthat any particular order be inferred.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the disclosed embodiments. Since modificationscombinations, sub-combinations and variations of the disclosedembodiments incorporating the spirit and substance of the embodimentsmay occur to persons skilled in the art, the disclosed embodimentsshould be construed to include everything within the scope of theappended claims and their equivalents.

As noted above, cable 120 and/or thin-film binder 128 may becables/binders as disclosed in U.S. application Ser. No. 13/790,329,filed Mar. 8, 2013, which is incorporated herein by reference in itsentirety. In one embodiment, a fiber optic cable includes a core and abinder film. The core includes a central strength member and coreelements, such as buffer tubes containing optical fibers, where the coreelements are stranded around the central strength member in a pattern ofstranding including reversals in lay direction of the core elements. Thebinder film is in radial tension around the core such that the binderfilm opposes outwardly transverse deflection of the core elements.Further, the binder film loads the core elements normally to the centralstrength member such that contact between the core elements and centralstrength member provides coupling therebetween, limiting axial migrationof the core elements relative to the central strength member.

Cable 120 may be an outside-plant loose tube cable, an indoor cable withfire-resistant/retardant properties, an indoor/outdoor cable, or anothertype of cable, such as a datacenter interconnect cable withmicro-modules or a hybrid fiber optic cable including conductiveelements. According to an exemplary embodiment, the cable 120 includes a(e.g., sub-assembly, micro-module), which may be located in the centerof the cable 120 or elsewhere and may be the only core of the cable 120or one of several cores. According to an exemplary embodiment, the coreof the cable 110 includes core elements. The core elements of cable 120include a tube, such as a buffer tube 20 surrounding at least oneoptical fiber 18, a tight-buffer surrounding an optical fiber, or othertube. According to an exemplary embodiment, the tube 20 may contain two,four, six, twelve, twenty-four or other numbers of optical fibers 18. Incontemplated embodiments, the core elements of cable 120 additionally oralternatively include a tube 20 in the form of a dielectric insulatorsurrounding a conductive wire or wires, such as for a hybrid cable.

In some embodiments, the tube 20 further includes a water-blockingelement, such as gel (e.g., grease, petroleum-based gel) or an absorbentpolymer (e.g., super-absorbent polymer particles or powder). In somesuch embodiments, the tube 20 includes yarn carrying (e.g., impregnatedwith) super-absorbent polymer, such as at least one water-blocking yarn,at least two such yarns, or at least four such yarns per tube 20. Inother contemplated embodiments, the tube 20 includes super-absorbentpolymer without a separate carrier, such as where the super-absorbentpolymer is loose or attached to interior walls of the tube 20. In somesuch embodiments, particles of super-absorbent polymer are partiallyembedded in walls of the tube 20 (interior and/or exterior walls of thetube) or bonded thereto with an adhesive. For example, the particles ofsuper-absorbent polymer may be pneumatically sprayed onto the tube 20walls during extrusion of the tube 20 and embedded in the tube 20 whilethe tube 20 is tacky, such as from extrusion processes. According to anexemplary embodiment, the optical fiber 18 of the tube 20 is a glassoptical fiber, having a fiber optic core surrounded by a cladding. Somesuch glass optical fibers may also include one or more polymericcoatings. The optical fiber 18 of the tube 20 is a single mode opticalfiber in some embodiments, a multi-mode optical fiber in otherembodiments, a multi-core optical fiber in still other embodiments. Theoptical fiber 18 may be bend resistant (e.g., bend insensitive opticalfiber, such as CLEARCURVE™ optical fiber manufactured by CorningIncorporated of Corning, N.Y.). The optical fiber 18 may be color-coatedand/or tight-buffered. The optical fiber 18 may be one of severaloptical fibers aligned and bound together in a fiber ribbon form.

According to an exemplary embodiment, the core of the cable 120 includesa plurality of additional core elements (e.g., elongate elementsextending lengthwise through the cable 120), in addition to the tube 20,such as at least three additional core elements, at least fiveadditional core elements. According to an exemplary embodiment, theplurality of additional core elements includes at least one of a fillerrod and/or an additional tube 20′. In other contemplated embodiments,the core elements of cable 120 may also or alternatively includestraight or stranded conductive wires (e.g., copper or aluminum wires)or other elements. In some embodiments, the core elements are all aboutthe same size and cross-sectional shape (see FIG. 6), such as all beinground and having diameters of within 10% of the diameter of the largestof the core element of cable 120. In other embodiments, core elements ofcable 120 may vary in size and/or shape.

As noted above, the cable 120 includes a binder film 128 (e.g.,membrane) surrounding the core of cable 120, exterior to some or all ofthe core elements of cable 120. The tubes 20 and any additional coreelements are at least partially constrained (i.e., held in place) anddirectly or indirectly bound to one another by the binder film 128. Insome embodiments, the binder film 128 directly contacts the coreelements of cable 120. For example, tension in the binder film 128, forexample circumferential tension, may hold the core elements against acentral strength member 24 and/or one another. The loading of the binderfilm 128 may further increase interfacial loading (e.g., friction)between the core elements with respect to one another and othercomponents of the cable 120, thereby constraining the core elements ofcable 120. According to an exemplary embodiment, the binder film 128includes (e.g., is formed from, is formed primarily from, has someamount of) a polymeric material such as polyethylene (e.g., low-densitypolyethylene, medium density polyethylene, high-density polyethylene),polypropylene, polyurethane, or other polymers. In some embodiments, thebinder film 128 includes at least 70% by weight polyethylene, and mayfurther include stabilizers, nucleation initiators, fillers,fire-retardant additives, reinforcement elements (e.g., choppedfiberglass fibers), and/or combinations of some or all such additionalcomponents or other components.

According to an exemplary embodiment, the binder film 128 is formed froma material having a Young's modulus of 3 gigapascals (GPa) or less,thereby providing a relatively high elasticity or springiness to thebinder film 128 so that the binder film 128 may conform to the shape ofthe core elements and not overly distort the core elements, therebyreducing the likelihood of attenuation of optical fibers 18corresponding to the core elements. In other embodiments, the binderfilm 128 is formed from a material having a Young's modulus of 5 GPa orless, 2 GPa or less, or a different elasticity, which may not berelatively high. According to an exemplary embodiment, the binder film128 is thin, such as 0.5 mm or less in thickness (e.g., about 20 mil orless in thickness, where “mil” is 1/1000th inch). In some suchembodiments, the film 128 is 0.2 mm or less (e.g., about 8 mil or less),such as greater than 0.05 mm and/or less than 0.15 mm. In someembodiments, the binder film 128 is in a range of 0.4 to 6 mil inthickness, or another thickness. In contemplated embodiments, the filmmay be greater than 0.5 mm and/or less than 1.0 mm in thickness. In somecases, for example, the binder film 128 has roughly the thickness of atypical garbage bag. The thickness of the binder film 128 may be lessthan a tenth the maximum cross-sectional dimension of the cable, such asless than a twentieth, less than a fiftieth, less than a hundredth,while in other embodiments the binder film 128 may be otherwise sizedrelative to the cable cross-section. In some embodiments, when comparingaverage cross-sectional thicknesses, the jacket 12 is thicker than thebinder film 128, such as at least twice as thick as the binder film 128,at least ten times as thick as the binder film 128, at least twentytimes as thick as the binder film 128. In other contemplatedembodiments, the jacket 12 may be thinner than the binder film 128, suchas with a 0.4 mm nylon skin-layer jacket extruded over a 0.5 mm binderfilm.

The thickness of the binder film 128 may not be uniform around the boundstranded elements of cable 120. Applicants have found some migration ofthe material of the binder film 128 during manufacturing. For example,the belts (e.g., treads, tracks) of a caterpuller used to impartcompressive forces on the binder film 128 that may somewhat flatten thebinder film 128 on opposing sides thereof, as the binder film 128solidifies and contracts to hold the stranded core elements to thecentral strength member 24. As such, the “thickness” of the binder film128, as used herein, is an average thickness around the cross-sectionalperiphery. For example, the somewhat flattened portions of the binderfilm 128 caused by the caterpuller may be at least 20% thinner than theadjoining portions of the binder film 128 and/or the average thicknessof the binder film 128.

Use of a relatively thin binder film 128 allows for rapid cooling (e.g.,on the order of milliseconds) of the binder film 128 duringmanufacturing and thereby allowing the binder film 128 to quickly holdthe core elements of cable 120 in place, such as in a particularstranding configuration, facilitating manufacturing. By contrast,cooling may be too slow to prevent movement of the stranded coreelements when extruding a full or traditional jacket over the core,without binder yarns (or the binder film); or when even extruding arelatively thin film without use of a caterpuller (sometimes called a“caterpillar”) or other assisting device. However such cables arecontemplated to include technology disclosed herein (e.g., coextrudedaccess features, embedded water-swellable powder, etc.) in someembodiments. Subsequent to the application of the binder film 128, themanufacturing process may further include applying a thicker jacket 12to the exterior of the binder film 128, thereby improving robustnessand/or weather-ability of the cable 120. In other contemplatedembodiments, the core of cable 120, i.e., the portion surrounded by thebinder film 128, may be used and/or sold as a finished product.

As shown in FIG. 1 and FIG. 6, the cable 120 further includes thecentral strength member 24, which may be a dielectric strength member,such as an up-jacketed glass-reinforced composite rod. In otherembodiments, the central strength member 24 may be or include a steelrod, stranded steel, tensile yarn or fibers (e.g., bundled aramid), orother strengthening materials. In one embodiment, the central strengthmember 24 includes a center rod and is up-jacketed with a polymericmaterial (e.g., polyethylene, low-smoke zero-halogen polymer).

According to an exemplary embodiment, powder particles, such assuper-absorbent polymer and/or another powder (e.g., talc), or anotherwater-absorbing component (e.g., water-blocking tape, water-blockingyarns) are attached to the outer surface of the central strength member24. At least some of the powder particles may be partially embedded inthe up-jacket of central strength member 24, and attached thereto bypneumatically spraying the particles against the up-jacket while the upjacket is in a tacky and/or softened state. The powder particles mayincrease or otherwise affect coupling between the central strengthmember 24 and the core elements of cable 120 around the central strengthmember 24.

Alternatively or in addition thereto, the particles may be attached tothe up jacket of central strength member 24 with an adhesive. In someembodiments, the central strength member 24 includes the rod without anup-jacket, and the particles may be attached to the unjacketed rod. Incontemplated embodiments, a strength member, such as a glass-reinforcedrod or up-jacketed steel rod, includes super-absorbent polymer or otherparticles attached to the outer surface thereof, as disclosed above,without the strength member being a central strength member.

In some embodiments, the core elements of cable 120 are stranded (i.e.,wound) about the central strength member 24. The core elements of cable120 may be stranded in a repeating reverse-oscillatory pattern, such asso-called S-Z stranding (see generally FIG. 1) or other strandingpatterns (e.g., helical). The binder film 128 may constrain the coreelements of cable 120 in the stranded configuration, facilitatingmid-span or cable-end access of the optical fibers 18 and cable bending,without the core elements releasing tension by expanding outward fromthe access location or a bend in the core of the cable 120.

In other contemplated embodiments, the core elements of the cable 120are non-stranded. In some such embodiments, the core elements of thecable 120 include micro-modules or tight-buffered optical fibers thatare oriented generally in parallel with one another inside the binderfilm 128. For example, harness cables and/or interconnect cables mayinclude a plurality of micro-modules, each including optical fibers andtensile yarn (e.g., aramid), where the micro-modules are bound togetherby the binder film 128. Some such cables may not include a centralstrength member. Some embodiments, include multiple cores orsub-assemblies, each bound by a binder film 128, and jacketed togetherin the same carrier/distribution cable, possibly bound together withanother binder film. For some such embodiments, techniques disclosedherein for rapid cooling/solidification during extrusion and inducingradial tension in the binder film 128 for coupling to a central strengthmember 24 may be unnecessary for manufacturing.

In some embodiments, the binder film 128 of the cable 120 includespowder particles, which may be used for providing water blocking and/orfor controlling coupling (e.g., decoupling) of adjoining surfaces in thecable 120. In some embodiments, the powder particles have an averagemaximum cross-sectional dimension of 500 micrometers (μm) or less, suchas 250 μm or less, 100 μm or less. Accordingly, the particles may belarger than water-blocking particles that may be used inside the tubes20, impregnated in yarns or embedded in interior walls of the tubes 20as disclosed above, which may have an average maximum cross-sectionaldimension less than 75 μm, to mitigate optical fiber micro-bendattenuation.

In some embodiments, at least some of the powder particles are coupleddirectly or indirectly to the binder film 128 (e.g., attached bounddirectly thereto, adhered thereto, in contact therewith), such ascoupled to a surface of the binder film 128, coupled to an exteriorsurface of the binder film 128, coupled to an outside surface of thebinder film 128 and/or an inside surface of the binder film 128.According to an exemplary embodiment, at least some of the powderparticles are partially embedded in the binder film 128, such as passingpartly through a surrounding surface plane of the binder film 128 whilepartially projecting away from the surface of the binder film 128; or,put another way, having a portion thereof submerged in the binder film128 and another portion thereof exposed. In some embodiments, a rotatingdie may be used to increase normal force on the tubes.

The powder particles may be attached to the binder film 128 bypneumatically spraying the powder particles onto the binder film 128,into and outside of the associated extrusion cone formed duringextrusion of binder film 128. The pneumatic spraying may also facilitaterapid cooling of the binder film 128. In other embodiment, staticelectricity or other means may be used to motivate the powder particlesto embed in the binder film 128 or otherwise couple thereto. In otherembodiments, glues or other attachment means are used to attach thepowder particles to the binder film 128. Use of the binder film 128 as acarrier for super-absorbent polymer particles may remove need forwater-blocking tape between the core and cable components outside thecore, as well as remove need for binder yarn to hold the water-blockingtape in place. In still other embodiments, powder particles may bepresent but loose and/or not attached to the binder film 128. Incontemplated embodiments, the binder film 128 may be coated with acontinuous water-blocking material/layer, or may include other types ofwater-blocking elements or no water-blocking elements.

According to an exemplary embodiment, the powder particles includesuper-absorbent polymer particles, and the amount of super-absorbentpolymer particles is less than 100 grams per square meter of surfacearea (g/m²) of the respective component to which the powder particlesare coupled (central strength member 24 or binder film 128). In somesuch embodiments, the amount of super-absorbent polymer particles isbetween 20 and 60 g/m², such as between 25 and 40 g/m². According to anexemplary embodiment, the amount of super-absorbent polymer or otherwater-blocking elements used in the cable is at least sufficient toblock a one-meter pressure head of tap water in a one-meter length ofthe cable 120, according to industry standard water penetration tests,which may correspond to the above quantities, depending upon othercharacteristics of cable 120, such as interstitial spacing between coreelements.

According to an exemplary embodiment, at least some of the powderparticles are positioned on an inside surface of the binder film 128between the binder film 128 and the core elements of cable 120. Inaddition to blocking water, such placement may mitigate adhesion betweenthe binder film 128 and the core elements during manufacturing of thecable 120, such as if the binder film 128 is tacky from extrusion orother manufacturing approaches, such as laser welding or heat softening.Alternatively or in combination therewith, in some embodiments, at leastsome of the powder particles are positioned on an outside surface of thebinder film 128.

Powder particles positioned on the outside surface of the binder film128 may provide water blocking between the binder film 128 andcomponents of the cable 120 exterior thereto, such as metal ordielectric armor 30 (FIG. 1) or micro-modules outside the core of cable120. The armor 30, as shown in FIG. 1, may be corrugated steel oranother metal and may also serve as a ground conductor, such as forhybrid fiber optic cables having features disclosed herein. Use of afilm binder, instead of a thicker layer, allows a narrower “light armor”design, where there is no jacket between the armor 30 and the core ofthe cable. Alternatively, the armor 30 may be dielectric, such as formedfrom a tough polymer (e.g., some forms of polyvinyl chloride).

According to an exemplary embodiment, embedded material discontinuities,such as easy access features 70 in the jacket 12, such as narrow stripsof co-extruded polypropylene embedded in a polyethylene jacket 12, mayprovide tear paths to facilitate opening the jacket 12. Alternatively,ripcords in or adjoining the jacket 12 may facilitate opening the jacket12.

In some embodiments, the jacket 12 and binder film 128 may blendtogether during extrusion of the jacket 12 over the binder film 128,particularly if the jacket 12 and the binder film 128 are formed fromthe same material without powder particles therebetween. In otherembodiments, the jacket 12 and the binder film 128 may remain separatedor at least partially separated from one another such that each isvisually distinguishable when the cable 120 is viewed in cross-section.In some embodiments, the binder film 128 and the jacket 12 are notcolored the same as one another. For example, they may be colored withvisually distinguishable colors, having a difference in “value” in theMunsell scale of at least 3. For example, the jacket 12 may be blackwhile binder film 128 may be white or yellow, but both including (e.g.,primarily consisting of, consisting of at least 70% by weight)polyethylene.

In some contemplated embodiments, the jacket 12 is opaque, such ascolored black and/or including ultra-violet light blocking additives,such as carbon-black; but the binder film 128 is translucent and/or a“natural”-colored polymer, without added color, such that less than 95%of visible light is reflected or absorbed by the binder film 128.Accordingly, in at least some such embodiments, upon opening or peelingback the jacket 12 away from the binder film 128 and the core of cable120, the tube 20 and at least some of the plurality of additional coreelements are at least partially visible through the binder film 128while being constrained thereby with the binder film 128 unopened andintact, such as visible upon directing light from a 25 watt whitelight-bulb with a 20-degree beam directly on the binder film 128 from adistance of one meter or less in an otherwise unlit room. Incontemplated embodiments, the core includes a tape or string (e.g.,polymeric ripcord), beneath the binder film 128 and visible through thebinder film 128, which may include indicia as to contents of the core ora particular location along the length of the cable 120.

According to an exemplary embodiment, the binder film 128 is continuousperipherally around the core, forming a continuous closed loop (e.g.,closed tube) when viewed from the cross-section, as shown in FIG. 6 forexample, and is also continuous lengthwise along a length of the cable120, where the length of the cable 120 is at least 10 meters (m), suchas at least 100 m, at least 1000 m, and may be stored on a large spool.In other contemplated embodiments, the cable 120 is less than 10 m long.

In some embodiments, around the cross-sectional periphery of the binderfilm 128, the binder film 128 takes the shape of adjoining core elementsand extends in generally straight paths over interstices between thecore elements, which may, in some embodiments, result in a generallypolygonal shape of the binder film 128 with rounded vertices, where thenumber of sides of the polygon corresponds to the number of adjoiningcore elements.

In some embodiments, the binder film 128 arcs into the intersticesbetween core elements so that the binder film 128 does not extendtangentially between adjoining core elements, but instead undulatesbetween concave arcs and convex arcs around the periphery of thestranded core elements and intermediate interstices. The concave arcsmay not be perfect circular arcs, but instead may have an average radiusof curvature that is greater than the radius of one or all of thestranded core elements and/or the central strength member 24. Putanother way, the degree of concavity of the concave arcs is less thanthe degree of convexity of the convex arcs. Applicants theorize that theundulation between concave arcs and convex arcs constrains the strandedcore elements, opposing unwinding of the stranded core elements aboutthe central strength member 24. Applying a vacuum to the interior of theextrusion cone used to form binder file 128 may increase the draw-downrate of the extrudate, and may facilitate formation of the concave arcs.Applicants further believe that the undulation and concave arcs increasethe torsional stiffness of the binder film 128.

Use of a continuous binder film 128 may block water from being able toreach the core of cable 120. In other embodiments, the binder film 128includes pinholes or other openings. In some contemplated embodiments,binder films may be extruded in a criss-crossing net mesh pattern offilm strips, or as a helical or counter-helical binder film strip(s),such as via rotating cross-heads or spinnerets. Either the core or thecross-head may be rotated, and the core may be rotated at a differentrate than the cross-head, or vice versa. In other contemplatedembodiments, a pre-formed curled or C-shaped tube may be used as thebinder 128, where the core is bound thereby.

In some embodiments the binder film 128 is in tension around the core ofcable 120, where hoop stress is spread relatively evenly around thetransverse (i.e., cross-sectional) periphery of the binder film 128where the binder film 128 overlays (e.g., contacts directly orindirectly) elements of the core of cable 120. As such, the binder film128 opposes outwardly transverse deflection of the core elementsrelative to the rest of the cable 120, such as outward torsional springforce of S-Z stranded core elements, buckling deflection of un-strandedcore elements, such as flat fiberglass yarns, or other loading. As such,the tension in the binder film 128 may improve cable stability andintegrity, such as in compression of the cable 120. In one embodiment,the binder film 128 is able to cool and constrict to a degree thatapplies a load to the stranded core elements of cable 120 thatcompresses the core elements (e.g., buffer tube 20) against the centralstrength member 24, providing coupling therebetween.

In some embodiments, the tension of the binder film 128 has adistributed loading of at least 5 newtons (N) per meter (m) length ofthe cable 120, which may be measured by measuring the average diameterof an intact binder film 128 surrounding the core elements, then openingthe binder film 128, removing the core elements, allowing time for thebinder film 128 to contract to an unstressed state (e.g., at least aday, depending upon material) at constant temperature, then measuringthe decrease in binder film 128 widthwise dimension (i.e., compared tothe average periphery). The tension is the loading required to stretchthe binder film 128 to the original width.

In various embodiments, thermoplastics and/or materials other thanpolyethylene may be used to form the binder film 128. The binder film128 may be of various colors, and may have UV stabilizers that permitthe binder film 128 as the exterior of a finished outdoor product. Thebinder film 128 may be printed upon. The binder film 128 may includetear or easy access features, such as those as disclosed herein withregard to the jacket 12. In some embodiments, the binder film 128 maysurround a broad range of different types of stranded cable components,such as S-Z stranded tight-buffered fibers, filler rods, fiberglassyarns, aramid yarns, and other components. According to an exemplaryembodiment, the cable 120 includes a dielectric armor layer, such asarmor 30, beneath the jacket 12, between the jacket 12 and the coreelements of cable 120.

According to an exemplary embodiment, the material of the binder film128 may be selected such that the melting temperature of the material ofthe binder film 128 is less (e.g., at least 30° C. less, at least 50° C.less) than the extrusion temperature (e.g., about 200-230° C.±20° C.) ofa jacket 12 that is subsequently extruded over the binder film 128. Insome such embodiments, the binder film 128 melts or blends into thejacket 12. In other embodiments, the binder film 128 maintainsseparation from the jacket 12 by intermediate material, such assuper-absorbent polymer particles. Applicants theorize that a reason thestranded core elements of cable 120 do not migrate axially or outwardlyduring extrusion of the jacket 12, while melting or softening of thebinder film 128, is that, by the time of subsequent extrusion of thejacket 12 (e.g., at least 2 seconds following stranding and applicationof the binder film 128, at least 5 seconds, at least 10 minutes), thestranded core elements of cable 120 have sufficiently conformed to thegeometry of the stranding pattern due to stress relaxation of thematerials of the stranded core elements, reducing spring forcesinitially carried by the stranded elements upon stranding; andApplicants theorize that the jacket 12 positively contributes to radialtension applied by the binder film 128 to constrain and normally loadthe core elements to the central strength member 24.

Further, Applicants have found that application of the binder film 128at extrusion temperatures above the melting temperature of the strandedcore elements (e.g., at least 30° C. above, at least 50° C. above) doesnot melt or substantially deform the stranded elements. As such, thebinder film 128 may include the same or similarly-melting polymers asbuffer tubes 20, stranded in the core, such as polypropylene. Further,Applicants have found very little or no sticking between the binder film128 and buffer tubes 20 stranded in the core of cable 120.

Further, Applicants have found that the greater strength ofpolypropylene relative to polyethylene allows the binder film 128 to bethinner for a polypropylene binder film 128 to provide the same amountof coupling force between the stranded core elements and the centralstrength member 24. For example, a 0.15 mm binder film 128 ofpolyethylene was found to have about a 70 N radial force, while a 0.15mm binder film 128 of polypropylene had about an 85 N radial force.However, polyethylene is typically considerably less expensive thanpolypropylene, and in other embodiments, polyethylene may be used forthe binder film 128.

In some embodiments, the binder film 128 is formed from a first materialand the jacket 12 is formed from a second material. The second materialof the jacket 12 may include, such as primarily include (>50% byweight), a first polymer such as polyethylene or polyvinyl chloride; andthe first material of the binder film 128 may include, such as primarilyinclude, a second polymer, such as polypropylene. In some embodiments,the first material further includes the first polymer (e.g., at least 2%by weight of the first material, at least 5% by weight, at least 10% byweight, and/or less than 50% by weight, such as less than 30% byweight). Inclusion of the first polymer in the first material of thebinder film 128, in addition to primarily including the second polymerin the first material, may facilitate bonding between the first andsecond materials so that the binder film 128 may be coupled to thejacket 12 and automatically removed from the core of cable 120 when thejacket 12 is removed from the core, such as at a mid-span accesslocation.

Using pull-through testing, Applicants have found that the binder film128, as disclosed herein, results in a (net) static friction forcebetween the stranded core elements of cable 120 and the central strengthmember 24 of at least 10 N for a 100 mm length of stranded elements,such as at least 15 N. Via pull-through testing, Applicants have foundthat the magnitude of the static friction force is related to thethickness of the binder film 128. For a polypropylene binder film 128 ofat least 0.02 mm but less than 0.04 mm in average wall thickness, thestatic friction force for a 100 mm section of stranded core elements(without a jacket) is at least 10 N, such as about 12.4 N, and/or theaverage static friction force for a 200 mm section of stranded coreelements is at least 20 N, such as about 23.1 N. Accordingly, for such abinder film 128, the reverse-oscillatory stranding pattern must be suchthat the net spring force of the stranded core elements is about 10 N orless for a 100 mm section to prevent axial migration of the strandedcore elements and formation of a “bird nest” during manufacturing.Applicants have also found, for a polypropylene binder film 128 of atleast 0.08 mm but less than 0.15 mm in average wall thickness, theaverage static friction force for a 100 mm section of stranded elementsis at least 20 N, such at least 30 N, and/or the average static frictionforce for a 200 mm section of stranded elements is at least 40 N, suchas at least 50 N. Some testing included stranded elements bound by bothbinder film 128 and binders yarns to determine the contribution of thebinder film 128.

In some embodiments, a stranded core of a cable, such as cable 120,includes a binder film 128 that constrains the stranded core elementshaving a reversal. In some embodiments, the core may be enclosed withina jacket, such as jacket 12. Binder film 128 is a thin polymericmaterial (e.g. polypropylene, polyethylene), which can be torn andpeeled back by hand to provide access to the stranded core elements andcentral strength member 24. Once released from the binder film 128, thestranded core elements may decouple from the central strength member 24.

In some embodiments, another advantage of the binder film 128 is thatstranded core elements can be accessed by opening the binder film 128,but without severing and/or removing lengthwise tension in the binderfilm 128. For example, a lengthwise incision is formed in the binderfilm 128, which may be guided by an interstice (i.e., open space, gap,groove) between stranded core elements. Due to the thinness of thebinder film 128, the incision can be made without specialize tools. Forexample, the incision in binder film 128 can be cut with scissors. Arazor blade, key, pocket knife or other common tools may also work. Thelengthwise incision in binder film 128 provides an opening through whichthe stranded core elements can be unwound at a reversal to provide extralength for handing the stranded elements, and one or more of theelements may be tapped at the mid-span location. For example, a buffertube 20 may be cut and pulled out of the opening formed by the incisionin binder film 128 so that optical fibers 18 can be accessed. At thesame time, the rest of the binder film 128 holds together and maintainstension forward and rear of the incision along the length of the cable120. Once access is no longer needed, the opening can be taped, shrinkwrapped, or otherwise secured and resealed. By contrast, binder yarnsmay need to be fully severed to access the stranded elements, releasingtension in the binder yarns.

What is claimed is:
 1. An optical communication cable, comprising: acore of the cable, comprising: optical fibers; buffer tubes surroundingsubsets of the optical fibers; and a central strength member, whereinthe buffer tubes are stranded around the central strength member in apattern of stranding including reversals in lay direction of the buffertubes; and a binder film to hold the buffer tubes in position around thecentral strength member, wherein using pull-through testing the binderfilm has a static friction force between the stranded buffer tubes andthe central strength member of at least 10 N for a 100 millimeter lengthof the stranded buffer tubes.
 2. The optical communication cable ofclaim 1, wherein the binder film comprises a polypropylene material. 3.The optical communication cable of claim 2, wherein the binder film hasan average wall thickness of at least 0.02 millimeters but less than0.04 millimeters.
 4. The optical communication cable of claim 3, whereinthe static friction force for a 200 millimeter section of strandedbuffer tubes is at least 20 N.
 5. The optical communication cable ofclaim 2, wherein the binder film has an average wall thickness of atleast 0.08 millimeters but less than 0.15 millimeters.
 6. The opticalcommunication cable of claim 5, wherein the static friction force forthe 100 millimeter length of the stranded buffer tubes is at least 20 N.7. The optical communication cable of claim 6, wherein a static frictionforce for a 200 millimeter section of the stranded buffer tubes is atleast 40 N.